1. Field of the Invention
The present invention relates to a semiconductor device and to a method of fabricating the same. More particularly, the present invention relates to an integrated circuit having a line type of pattern and to a method of fabricating the same
2. Description of the Related Art
The design rule of a line type of circuit pattern of today's highly integrated semiconductor devices is now at a deep sub-micron level. However, the lines of an integrated circuit having a design rule on this low of an order are prone to experiencing serious RC delays. Therefore, a high fusion point metal, such as tungsten, having low sheet resistance has been used to form the lines of the circuit patterns. In particular, high fusion point metals have been used to form gate electrodes, bit lines, and other parts of a line type of circuit pattern.
However, a gate insulating film of a semiconductor device may be contaminated if only a high fusion point metal layer were used to form the gate electrode of the device. Accordingly, a gate electrode typically will have a stacked structure which includes a gate line made of polycrystalline silicon doped with impurities, and a line of the high fusion point metal disposed on the polycrystalline gate line. Also, a barrier layer is formed between the polycrystalline silicon gate line and the metal layer to prevent a layer of silicide from forming at the interface between the polycrystalline silicon and the high fusion point metal layer during a subsequent heat treatment process. However, the relatively great interfacial resistance between the barrier layer and the poly-crystalline silicon compromises the response time of the semiconductor device. A lower interfacial resistance can be provided by forming an ohmic layer between the polycrystalline silicon and the metal layer.
In light of the above, a typical gate electrode is fabricated by sequentially performing deposition processes to form poly-crystalline silicon, ohmic, barrier, and metal layers, patterning the layers, and subjecting the layers to an oxidation process. The oxidation process cures defects or eliminates hot carriers which may occur in some of the layers during the fabricating process.
However, the oxidation of the barrier layer as a result of this oxidation process reduces the overall quality of the semiconductor device.